419919544-Earths-Interior.ppt

The Earth’s Interior By: Junard A. Asentista  Learning Competencies/Objectives: In this module, you should be able to: 1. Describe the internal structure of the Earth. 2. Discuss the possible causes of plate movement. 3. Enumerate the lines of evidence that support plate...

The Earth’s Interior By: Junard A. Asentista  Learning Competencies/Objectives: In this module, you should be able to: 1. Describe the internal structure of the Earth. 2. Discuss the possible causes of plate movement. 3. Enumerate the lines of evidence that support plate movement.  ACTIVITY Graphic Organizer No. 1 Graphic Organizer No. 2 Graphic Organizer No. 3  Activity 1 Amazing Waves! Objectives: Define seismic waves scientifically. Differentiate the different types of seismic waves. Recognize the importance of seismic waves in the study of the Earth’s interior. Q1. Differentiate surface waves from body waves. Surface waves travel only on the Earth’s surface like ripples of water while body waves travel through the Earth’s body (interior). In addition, surface waves arrive last at seismic recording stations compared to the body waves. Q2. Which type of waves do you think were useful to seismologists in their study of the Earth’s interior? Explain your answer. The body waves were used by seismologists because they can pass through the Earth’s interior.  It takes different properties (like reflection and refraction properties of waves) and characteristics to analyze and differentiate the media where they travel through.  Studying the Earth’s Interior Scientists tried to explore and study the interior of the Earth. Yet, until today, there are no mechanical probes or actual explorations done to totally discover the deepest region of the Earth.  The Earth is made up of three layers: the crust, the mantle, and the core. The study of these layers is mostly done in the Earth’s crust since mechanical probes are impossible due to the tremendous heat and very high pressure underneath the Earth’s surface.  In Grade 8, it was mentioned that seismic waves from earthquakes are used to analyze the composition and internal structure of the Earth. What are seismic waves? Seismic waves are waves of energy that travel through the Earth’s layers, and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large man- made explosions that give out low-frequency acoustic energy.  Two main types of seismic waves Body waves Surface waves  Surface Waves Surface waves can only travel through the surface of the Earth. They arrive after the main P and S waves and are confined to the outer layers of the Earth.  Two types of surface waves Love waves Rayleigh waves  Love waves Love wave is named after A.E.H. Love, a British mathematician who worked out the mathematical model for this kind of wave in 1911.  It is faster than Rayleigh wave and it moves the ground in a side-to-side horizontal motion, like that of a snake’s causing the ground to twist. This is why Love waves cause the most damage to structures during an earthquake.  Rayleigh waves It was named after John William Strutt, Lord Rayleigh, who mathematically predicted the existence of this kind of wave in 1885.  A Rayleigh wave rolls along the ground just like a wave rolls across a lake or an ocean. Since it rolls, it moves the ground either up and down or side-to-side similar to the direction of the wave’s movement. Most of the shaking felt from an earthquake is due to the Rayleigh wave.  Body Waves Body waves can travel through the Earth’s inner layers. With this characteristic of the body waves, they are used by scientists to study the Earth’s interior. These waves are of a higher frequency than the surface waves.  Two types of body waves P-waves (primary waves) S-waves (secondary waves)  P-wave (primary wave) pulse energy that travels quickly through the Earth and through liquids travels faster than the S-wave After an earthquake, it reaches a detector first (the reason why it is called primary) also called compressional waves, travel by particles vibrating parallel to the direction the wave travel  They force the ground to move backward and forward as they are compressed and expanded. Most importantly, they travel through solids, liquids and gases.  S-wave (secondary wave or shear wave) a pulse energy that travels slower than a P-wave through Earth and solids move as shear or transverse waves, and force the ground to sway from side to side, in rolling motion that shakes the ground back and forth perpendicular to the direction of the waves  The idea that the S-waves cannot travel through any liquid medium led seismologists to conclude that the outer core is liquid. Figure1 shows the vibration directions of P and S-waves.  Scientists gained information about the Earth’s internal structure by studying how seismic waves travel through the Earth. - it involves measuring the time it takes for both types of waves to reach seismic wave detecting stations from the epicenter of an earthquake.  An epicenter is a point in the Earth’s surface directly above the focus. Since P-waves travel faster than S-waves, they’re always detected first. The farther away from the epicenter means the longer time interval between the arrival of P and S waves.  In 1909, Yugoslavian seismologist Andrija Mohorovičić (moh-haw-rohvuh- chich) found out that the velocity of seismic waves changes and increases at a distance of about 50 kilometers below the Earth’s surface. This led to the idea that there is a difference in density between the Earth’s outermost layer (crust) and the layer that lies below it (mantle). The boundary between these two layers is called Mohorovičić discontinuity in honor of Mohorovičić, and is short termed Moho.  P-waves can travel through liquids while S-waves cannot. During an earthquake, the seismic waves radiate from the focus. Based on figure on the right, the waves bend due to change in density of the medium. As the depth increases, the density also increases. The existence of a shadow zone, according to German seismologist Beno Gutenberg (ɡuː t ə n bɛʁk), could only be explained if the Earth contained a core composed of a material different from that of the mantle causing the bending of the P- waves. To honor him, mantle–core boundary is called Gutenberg discontinuity.  Beno Gutenberg  In 1936, the innermost layer of the Earth was predicted by Inge Lehmann, a Danish seismologist. He discovered a new region of seismic reflection within the core. So, the Earth has a core within a core. Based on Figure 3 on page 8, we can say that the outer part of the core is liquid based from the production of an S wave shadow and the inner part must be solid with a different density than the rest of the surrounding material.  Let’s Fit it! Objectives: Find clues to solve a problem. Recognize how the Continental Drift Theory is developed. Q10. What features of the newspaper helped you to connect the pieces perfectly? Answer: Pictures and words in the newspaper helped us to connect the pieces perfectly. Q11. How do the lines of prints or texts in the newspaper help you to confirm that you have reassembled the newspaper/magazine page? Answer: The lines of prints make sure that the newspaper is fitted well. The words written serve as clues in connecting the pieces of newspaper together. The completed/connected words confirm that the newspaper has been reassembled. Q12. Show proofs that the newspaper is perfectly reassembled. Answer: - The picture in the newspaper if completed. - The broken words were completed/connected.  In 1912, Alfred Wegener (pronounced as vey-guh-nuhr), a German meteorologist, proposed a theory that about 200 million years ago, the continents were once one large landmass.  He called this landmass Pangaea, a Greek word which means “All Earth.” Figure 7 shows how Pangaea evolved into how the continents look today. This Pangaea started to break into two smaller supercontinent called Laurasia and Gondwanaland during the Jurassic Period. These smaller supercontinents broke into the continents and these continents separated and drifted apart since then. s Evidence: The Continental Jigsaw Puzzle Did it really start as one big landmass?  It seems very impossible that the seven continents, which are currently thousands of miles away from each other were actually connected pieces of a supercontinent.  The most visible and fascinating evidence that these continents were once one is their shapes. The edge of one continent surprisingly matches the edge of another: South America and Africa fit together; India, Antarctica, and Australia match one another; Eurasia and North America complete the whole continental puzzle in the north. Evidence from Fossils Distribution of Fossils across Different Continents Glossopteris Fossil  Could it be possible that they existed in this region where temperature was very low? Or could it be possible that, long before, Antarctica was not in its Mesosaurus Fossil current position? Evidence from Rocks  Fossils found in rocks support the Continental Drift Theory. The rocks themselves also provide evidence that continents drifted apart from each other. From the previous activity, you have learned that Africa fits South America. Rock formations in Africa line up with that in South America as if it was a long mountain range.  Coal Deposits Coal beds were formed from the compaction and decomposition of swamp plants that lived million years ago. These were discovered in South America, Africa, Indian subcontinent, Southeast Asia, and even in Antarctica.  The current location of Antarctica could not sustain substantial amount of life. If there is a substantial quantity of coal in it, thus, it only means that Antarctica must have been positioned in a part of the Earth where it once supported large quantities of life. This leads to the idea that Antarctica once experienced a tropical climate, thus, it might have been closer before to the equator. The Seafloor Spreading